Oil pump for oil circuit breaker

ABSTRACT

An oil pump used with an oil circuit breaker for pumping oil through the arc drawn as the contacts of the breaker open to extinguish the arc. The pump includes a piston and a spring charged by a closing operation of the circuit breaker for pumping oil from an oil filled cavity in the cylinder through a second cavity in the cylinder and into the arc. The piston means is positioned within the oil filled cavity and a disc mounted on the piston means moves through a restricted portion of the second cavity having openings therein for discharge of the oil from the pump. However, the oil is confined in the oil filled cavity and movement of the piston means in pumping oil to the arc is delayed until the disc passes the openings in the restricted portion.

United States Patent 11* r 5 ,1; I, 1)! l' 61' Primary Examiner-Robert S. Macon Attorney-Richard C. Ruppin ABSTRACT: An oil pump used with an oil circuit breaker for pumping oil through the are drawn as the contacts of the breaker open to extinguish the arcfThe pump includes a piston and a spring charged by a closing operation of the circuit breaker for pumping oil from an oil filled cavity in the cylinder through a second cavity in the cylinder and into the arc. The piston means is positioned within the oil filled cavity and a disc mounted on the piston means moves through a restricted portion ofthe second cavity having openings therein for discharge of the oil from thepump. However, the oil is confined in the oil filled cavity and movement of the piston means in pumping oil to the arc is delayed until the disc passes the openings in the restricted portion.

OIL PUMP FOR OIL CIRCUIT BREAKER BACKGROUND OF THE INVENTION This invention relates to an oil pump for a circuit interrupter and in particular to an oil pump for pumping pressurized oil through an are formed by the contacts of the circuit interrupter to extinguish the arc.

Due to the very high voltages increasingly being used in alternating current power systems, interrupting problems including interruption of arcs in circuit breakers have become quite critical. The arm interruption problem is intensified because such high-voltage power systems have the inherent ability to swing through a phase opposition angle such that the system on either side of the breaker can be 180 out of phase at the instant the interrupter is required to open. In this maximum situation, the potential available on a line to ground basis is 2.5 times the normal maximum line to ground voltage including a 25 percent overshoot. For example, in a situation where the normal line to ground voltage is 140 kv., the voltage at the circuit interrupter may be 350 kv. line to ground. At this voltage, circuit breaker components such as shunting resistors become extremely overstressed and the arc across the breaker contacts connected to the shunting resistor becomes extremely difficult to extinguish.

To aid in extinguishing this arc, dielectric oil may be pumped through the are by an auxiliary oil pump operated in conjunction with an opening operation of the circuit breaker. It is desirable that the pumping of oil be delayed until late in the opening stroke during a breaker opening operation so that the extinguishing action of the oil will occur at the most efficient time. Another desirable feature based on commercial requirements is that any particular oil pump be suitable for use with a number of different sizes and types of circuit breaker. To this end, it is usually necessary that the time at which the pumping of the oil through the arc takes place be variable due to different contact spacings and other structural and operational differences of different interrupter sizes and types.

SUMMARY OF THE INVENTION It is an object of the invention to provide in an oil circuit breaker an economical and simple oil pump for pumping oil through the are formed between contacts during an opening operau'on of the breaker at a time which will most efficiently extinguish the arc. It is also an object of the invention to provide such an oil pump which pumps oil at any one of a preselected plurality of time intervals during a circuit breaker opening operation.

The objects of the invention are accomplished by providing, in an oil circuit breaker, an oil pump having first and second cavities or chambers connected by an orifice and a restricted chamber portion connected to the orifice in the second cavity. Dielectric oil is in the first cavity and the restricted chamber and second cavity both contain openings permitting the oil in the first cavity to flow through the orifice into the restricted chamber and out of the openings in the restricted chamber and the second cavity. Piston means and resilient means are positioned within the first cavity in a manner such that the resilient means is charged in response to a circuit interrupter closing operation. The piston means and resilient means are released when the breaker opens so that the resilient means will move to an energy discharged condition and thereby move the piston to pump oil from the first cavity through the aforesaid openings to the are formed between the contacts of the interrupter. Pumping of the oil out of the openings is delayed by a member carried by the piston means and which is movable through the restricted chamber. Until the member moves past the openings in the restricted chamber, escape of the oil from the first cavity is retarded and will not be discharged to the arc. As the member passes the openings in the restricted chamber, the oil will escape from the first cavity under the pressure created by the piston means and resilient means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an oil circuit breaker including the oil pump according to the instant invention;

FIG. 2 shows an elevational view of the circuit breaker in an open position with a portion of the oil pump broken away;

FIG. 3 shows an elevational view of the circuit breaker in a closed position with a portion of the oil pump broke away; and

FIG. 4 shows an elevational view of the circuit breaker of FIGS. 2 and 3 during operation with a portion of the oil pump broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, a circuit breaker is shown having a metal tank 2 filled with a dielectric oil 4. A circuit breaker operating mechanism 6 and an interrupter assembly 8 are both mounted within tank 2. Bushings 10 extend from within the tank 2 to above the tank 2 and may be connected to a highvoltage power system (not shown). The interrupter assembly 8 includes fixed contact means 12, 13, and 14 each containing an interrupting chamber and a fixed contact, both of which are not shown but are well known in the art. The breaker operating mechanism 6 carries movable contacts 16, 17 and 18 so that when the operating mechanism 6 moves to a closed position each of the movable contacts 16-18 will be in engagement with a fixed contact within fixed contact means 12, 13 and 14 and when the operating mechanism 6 moves to an open position the movable contacts 16, 17 and 18 will be out of engagement with the fixed contacts. It may be noted that the operating mechanism 6 shown in FIG. 1 is only a half-pole assembly for one phase of the power system and that another, identical interrupter assembly containing contacts identical to those of interrupter assembly 8, is mounted within the tank 2 to the left of operating mechanism 6 as shown in FIG. 1. The contacts of interrupter assembly 8 and the other identical interrupter assembly are connected in series through conductors (not shown) in bushings 10 to the power system.

A resistor assembly 20 is also mounted within tank 2 and is electrically connected in shunt with the contacts within fixed contact means 12, 13 and 14 and the movable contacts 16, 17 and 18 so that the resistor assembly 20 carries the current after the contacts have been moved out of engagement by the breaker operating mechanism 6. This connection is in a manner well known in the art and is such that the final breaker current will be carried by the movable contact 18 and resistor assembly 20 and the final arc caused by this current occurs in the interrupting chamber of fixed contact means 14.

The breaker operating mechanism 6 is rotatably operable to move the movable contacts 16, 17 and 18 into engagement with the fixed contacts within fixed contact means 12, 13 and 14, respectively. To move the contacts out of engagement, the operating mechanism 6 is rotatable in the opposite direction to disengage the movable and fixed contacts. As the contacts are moved out of engagement with each other, an arc is drawn between each of the fixed and movable contact pairs. Because the arc in the interrupting chamber within fixed contact means 14 is the last arc that must be extinguished it will also be the most difficult arc to extinguish and, accordingly, assistance in extinguishing it is highly desirable.

In FIGS. 2-4, the oil pump is shown as including a cylinder 42 having cavities 44 and 46 and a wall 48 between and separating the cavities 44 and 46. The cylinder 42 is preferably of an electrically insulating material such as glass epoxy to prevent flashover between contacts through pump 40. An orifice 50 is provided in the wall 48 to connect the cavities 44 and 46. As shown in FIG. 3, when the operating mechanism 6 is in its closed position the cavities 44 and 46 of oil pump 40 are both filled with dielectric oil 4. The cavity 46 includes a restricted portion or inner chamber 30 having a wall 32, an outer chamber 34 and discharge holes 36 connecting the inner and outer chambers 30 and 34. Discharge means is provided for discharging the oil 4 to the interrupter chamber within contact means 14 and includes an opening 52 in the outer chamber 34 of cavity 46, hose 22 connecting the opening 52 to the interrupter chamber within contact means 14, resilient means or spring 54 within cavity 44 and piston means comprising piston 56 slidably supported within cavity 44 and piston rod 58 attached to the piston 56. The clamps 24 hold the hose 22 to the pump 40 and fixed contact means 14. The piston rod 58 extends through the orifice 50, the restricted portion 30 and an opening 60 in cavity 46 and includes a stop member 62 and a drive end 64. The spring 54 engages and is supported by the piston 56 and the end 38 of the cylinder 42. The spring 54 is shown in an extended, energy-discharged position in FIG. 2 and in a compressed, energy-stored position in FIG. 3. The spring 54 is moved from its energy-discharged condition shown in FIG. 2 when the roller 66 on the operating mechanism 6 engages drive end 64 of the piston rod 58 as operating mechanism 6 rotates to thereby drive the piston rod 58 and piston 56 to the right relative to the views of FIGS. 2-4. Oil intake holes 68 and 70 are provided in the cylinder 42 so that the oil 4 in the tank 2 flows into cavity 44 when the piston 56 is adjacent wall 48. When the piston 56 moves from its position adjacent wall 48 toward the end 38 of cylinder 42, a butterfly valve 80 on piston 56 opens to permit flow of oil 4 from the portion 72 to the portion 74 of cavity 44. Thus, the oil which flows into cavity 44 through holes 68 and 70 when the piston 56 is adjacent to wall 48, as shown in FIG. 2, fills the cavity 44 when the piston 56 is adjacent end 38 so that the oil 4 can be discharged through opening 52 when piston 56 is moved towards wall 423. A coil spring 82 is mounted on piston rod 58 to hold the butterfly valve 80 closed when the piston 56 is at end 38. The butterfly valve 80 is held closed when the piston 56 is moving toward the wall 48 by the pressure of the oil against the valve 80.

A delay mechanism for delaying movement of the piston 56 from its position adjacent! end 38 to its position adjacent wall 48 is provided and includes blocking means or member 84 mounted on the piston rod 58 and a spring 86 for holding the member 84 in position on piston rod 58. A disc 88 is affixed to the piston rod 58 for holding the springs 82 and 86 in a compressed condition. The member 84 may be adjusted to a plurality of different positions along the length of piston rod 58 by washer shims 90. The member $4 preferably is a disc having a cross-sectional shape substantially identical to the cross-sectional shape of the orifice 50 and restricted portion 30 and fitting through the orifice 50 and restricted portion 30 with minima clearance. Typically, the orifice 50 and member 84 are circular in shape. As shown in FIG. 2, when the interrupter operating mechanism 6 is in its open position and the piston rod 58 extends a maximum distance out of cylinder 42 corresponding to the position of the piston 56 adjacent to wall 48, the member 84 is stopped against the cylinder 42 and held away from shims 90 so that the spring 88 is highly compressed. When the circuit operating mechanism 6 is in it's closed position as shown in FIG. 3, the piston rod 58 is relatively withdrawn into the cylinder 42 in a position corresponding to the position of the piston 56 adjacent end 38 of the cylinder 42. In the latter position of the piston rod 58, the member 84 is positioned adjacent to or within the orifice 50, depending on the setting of the member 84 as determined by the shims 94).

The operation of the circuit breaker and oil pump 40 is described with reference to FiGS. 2-4. In FIG. 2, the operating mechanism 6 is shown in its open position in which roller 66 is out of engagement with piston rod 58 and the movable contacts 16, I7 and 18 are out of engagement with the fixed contacts within contact means l2, l3 and 14. The spring 54, which may be considered as an energy storage means, is in an energy-discharged condition and the piston 56 is adjacent to wall 48 and piston rod 58 is in its maximum extended position. The cavities 44 and 46 are both filled with oil 4. When operating mechanism 6 rotates, the roller 66 engages drive end 64 of piston rod 58 and moves piston 56 to a relatively withdrawn position within cylinder 42 in which the member 84 is adjacent or within the orifice 50 and the piston 56 is adjacent the end 38 so that the spring 54 is maintained in an energy stored condition (see FIG. 3). As the piston 56 moves toward the end 38 of cylinder 42, the butterfly valve opens as previously described to permit oil to flow through the piston into the portion 74 of cavity 44. As seen in FIG. 3, both cavities 44 and 46 continue to be filled with oil. In FIG. 4, the oil pump 40 is shown during an interrupting operation just after the operating mechanism 6 has moved to its open position. During an opening operation, the member 84 moves through the orifice 50 and restricted portion 30 to confine the oil in portion 74 of cavity 44 and prevent its escape through restricted portion 30, chamber 34, discharge holes 36, opening 52 and hose 22 until member 84 starts moving past holes 36. MOvement of member 84 and piston 56 as spring 54 discharges is permitted by leakage of oil 4 out of portion 74 through the clearance between member 84 and restricted portion 30. Since this clearance is quite small, escape of oil 4 and movement of member 84 and piston 56 will be retarded. As member 84 clears the holes 36, the oil 4 rapidly flows out of hose 22 so that the piston 56 quickly completes its movement toward wall 48.

By selecting the number of shims used to position member 84 on piston 58, the distance of travel of member 84 before clearing discharge holes 36 and thereby the amount of time delay before discharge of oil 4 to the arc in the interrupting chamber may be determined. This time delay may be measured in cycles of the alternating current power system and the shim 90 adjustments, may, for example, be in increments which permit a variation in time delay between 0 and 5 cycles per second.

While only asingle embodiment of the invention has been shown herein, it will be realized that many modifications thereof are feasible without departing from the spirit and scope of the invention. It is accordingly intended that the scope of the invention is not to be limited by the specific embodiment disclosed.

We claim:

1. In a circuit breaker including contact means drawing an arc during a breaker opening operation and operating means, the combination of a pump comprising:

a first member having first and second cavities positioned adjacent each other, said first cavity containing a dielectric fluid, said second cavity having a first opening therein for discharge of said fluid from the second cavity;

delay means responsive to an opening operation by said operating means for delaying discharge of said fluid from the second cavity, said delay means including a fixed member positioned between said cavities and having an orifice connecting the cavities, said second cavity having a restricted portion surrounding the orifice and having a second opening therein for discharge of said fluid from the first cavity, and blocking means movable through said orifice and restricted portion for retarding escape of the fluid within said first cavity until the blocking means moves past the second opening; and

discharge means operafively delayed in response to said delay means for discharging said fluid from the first cavity into said are to extinguish the arc whereby said fluid is discharged after said operating means operates to open said contact means and said arc is established.

2. The combination according to claim 1 wherein said discharge means includes piston means within said first member for pumping said fluid out of the first cavity through the restricted portion and said blocking means is mounted on said piston means.

3. The combination according to claim 2 wherein said discharge means includes energy storage means for moving said piston means and blocking means.

4. The combination according to claim 3 wherein:

said piston means comprises a piston movable within said first cavity; and

said energy storage means comprises resilient means engaging the piston means for moving said piston in a first direction and moving said blocking means through the orifice and restricted portion.

5. The combination according to claim 4 wherein:

said piston means extends out of said first member; and

said operating means is movable against the piston means in 5 a direction'opposite to the first direction to move said resilient means to a stored energy condition.

6. The combination according to claim it wherein said blocking means and restricted portion have a clearance therebetween for permitting leakage of fluid out of the first cavity.

7. in a circuit breaker having a pair of contacts and operating means supporting one of said contacts, said operating means being movable between an open position in which said contacts are out of engagement and a closed position in which said contacts are in engagement, said contacts drawing an arc therebetween when moved out of engagement, a pump comprising:

a cylinder member having first and second cavities posi tioned axially of each other, a wall between said cavities and having an orifice connecting the cavities, a restricted portion in said second cavity connected to said orifice, a first opening in the restricted portion, and a second opening in the second cavity;

a piston slidably supported in said first cavity and having a first position spaced from said wail and a second position adjacent said wall;

a piston rod attached to said piston and having a first posi- I tion corresponding to the first position of the piston and a second position corresponding to the second position of the piston, said piston rod engaging the operating means when in the second position and the operating means is in its ciosed position, said piston and piston rod being maintained in their first positions by the operating means;

dielectric fluid filling said first cavity when said piston is in its first position;

resilient means in said first cavity engaging said piston for moving the piston toward its second position and moving said piston rod through said orifice and restricted portion in response to movement of the operating means toward its open position whereby said fluid is discharged from the first cavity;

delay means mounted on said piston rod and including a member movable through said orifice and restricted portion as the piston rod moves toward its second position for confining fluid within the first cavity until said member is past the second opening to delay movement of the piston toward said wall and discharge of said fluid through the first and second openings until after said operating means has moved toward its open position and the contacts are out of engagement; and

means connected to said second opening for directing said fluid through said are to extinguish the are.

8. The combination according to claim 7 wherein said orifice and restricted portion have a predetermined cross-sectional shape and said member comprises a disc having a crosssectional shape substantially identical to the shape of the orifice and restricted portion.

9. The combination according to claim 7 wherein said delay means is adjacent said orifice when the piston is in its first position and said contacts are engaged, said delay means remaining adjacent said orifice while the piston is adjacent its first position subsequent to disengagement of the contacts and movement of the piston toward its second position by the resilient means.

10. The combination according to claim 9 wherein said member has a plurality of selectively predetermined positions on the piston whereby the time during which said fluid is confined within the first cavity and the delay of movement of the piston toward said wall may be varied.

H i. The combination according to claim 7 wherein:

said first cavity has first and second portions and said piston is between the two portions; and further comprising valve means mounte on said piston, said valve means connecting the two cavity portions when the piston is moved toward its first position whereby fluid from the first portion flows into the second portion, said valve means sealing the two portions when the piston is moved toward its second position whereby fluid flows through said orifice and restricted portion.

12. The combination according to claim ll wherein said resilient means comprises a helical spring in one of the portions of said first cavity.

13. The combination according to claim 12 wherein:

said member has a plurality of selectively different predetermined positions on the piston whereby the time during which said fluid is confined within the first cavity and the delay of movement of the piston toward said wall may be varied; and further comprising a resilient member mounted on the piston rod and engaging said member whereby the latter is held in the selected one of its positions. 

1. In a circuit breakEr including contact means drawing an arc during a breaker opening operation and operating means, the combination of a pump comprising: a first member having first and second cavities positioned adjacent each other, said first cavity containing a dielectric fluid, said second cavity having a first opening therein for discharge of said fluid from the second cavity; delay means responsive to an opening operation by said operating means for delaying discharge of said fluid from the second cavity, said delay means including a fixed member positioned between said cavities and having an orifice connecting the cavities, said second cavity having a restricted portion surrounding the orifice and having a second opening therein for discharge of said fluid from the first cavity, and blocking means movable through said orifice and restricted portion for retarding escape of the fluid within said first cavity until the blocking means moves past the second opening; and discharge means operatively delayed in response to said delay means for discharging said fluid from the first cavity into said arc to extinguish the arc whereby said fluid is discharged after said operating means operates to open said contact means and said arc is established.
 2. The combination according to claim 1 wherein said discharge means includes piston means within said first member for pumping said fluid out of the first cavity through the restricted portion and said blocking means is mounted on said piston means.
 3. The combination according to claim 2 wherein said discharge means includes energy storage means for moving said piston means and blocking means.
 4. The combination according to claim 3 wherein: said piston means comprises a piston movable within said first cavity; and said energy storage means comprises resilient means engaging the piston means for moving said piston in a first direction and moving said blocking means through the orifice and restricted portion.
 5. The combination according to claim 4 wherein: said piston means extends out of said first member; and said operating means is movable against the piston means in a direction opposite to the first direction to move said resilient means to a stored energy condition.
 6. The combination according to claim 1 wherein said blocking means and restricted portion have a clearance therebetween for permitting leakage of fluid out of the first cavity.
 7. In a circuit breaker having a pair of contacts and operating means supporting one of said contacts, said operating means being movable between an open position in which said contacts are out of engagement and a closed position in which said contacts are in engagement, said contacts drawing an arc therebetween when moved out of engagement, a pump comprising: a cylinder member having first and second cavities positioned axially of each other, a wall between said cavities and having an orifice connecting the cavities, a restricted portion in said second cavity connected to said orifice, a first opening in the restricted portion, and a second opening in the second cavity; a piston slidably supported in said first cavity and having a first position spaced from said wall and a second position adjacent said wall; a piston rod attached to said piston and having a first position corresponding to the first position of the piston and a second position corresponding to the second position of the piston, said piston rod engaging the operating means when in the second position and the operating means is in its closed position, said piston and piston rod being maintained in their first positions by the operating means; dielectric fluid filling said first cavity when said piston is in its first position; resilient means in said first cavity engaging said piston for moving the piston toward its second position and moving said piston rod through said orifice and restricted portion in response to movement of the operating means toward its open position whereby said fluid is discharged from the first cavity; delay means mounted on said piston rod and including a member movable through said orifice and restricted portion as the piston rod moves toward its second position for confining fluid within the first cavity until said member is past the second opening to delay movement of the piston toward said wall and discharge of said fluid through the first and second openings until after said operating means has moved toward its open position and the contacts are out of engagement; and means connected to said second opening for directing said fluid through said arc to extinguish the arc.
 8. The combination according to claim 7 wherein said orifice and restricted portion have a predetermined cross-sectional shape and said member comprises a disc having a cross-sectional shape substantially identical to the shape of the orifice and restricted portion.
 9. The combination according to claim 7 wherein said delay means is adjacent said orifice when the piston is in its first position and said contacts are engaged, said delay means remaining adjacent said orifice while the piston is adjacent its first position subsequent to disengagement of the contacts and movement of the piston toward its second position by the resilient means.
 10. The combination according to claim 9 wherein said member has a plurality of selectively predetermined positions on the piston whereby the time during which said fluid is confined within the first cavity and the delay of movement of the piston toward said wall may be varied.
 11. The combination according to claim 7 wherein: said first cavity has first and second portions and said piston is between the two portions; and further comprising valve means mounted on said piston, said valve means connecting the two cavity portions when the piston is moved toward its first position whereby fluid from the first portion flows into the second portion, said valve means sealing the two portions when the piston is moved toward its second position whereby fluid flows through said orifice and restricted portion.
 12. The combination according to claim 11 wherein said resilient means comprises a helical spring in one of the portions of said first cavity.
 13. The combination according to claim 12 wherein: said member has a plurality of selectively different predetermined positions on the piston whereby the time during which said fluid is confined within the first cavity and the delay of movement of the piston toward said wall may be varied; and further comprising a resilient member mounted on the piston rod and engaging said member whereby the latter is held in the selected one of its positions. 